Prior art mold assemblies such as shown in the Wilds et al. U.S. Pat. No. 3,473,197 typically include a relatively large yoke surrounding moveable side wall members or portions of the mold apparatus, this large yoke being included to provide support for the side wall members and to prevent outward deflection of the side wall members during injection of plastic material into the mold.
The provision of the large yoke surrounding the side wall members as shown in the Wilds et al. patent adds to the weight of the mold and increases the complexity of the mold apparatus. The provision of the large yoke also requires the construction of a large mold and the use of a large mold press or machine and therefore requires a large capital expenditure.
The Lovejoy U.S. Pat. No. 3,838,960 illustrates an effort to design a mold construction which eliminates the use of the large yoke surrounding the mold side walls. In the Lovejoy construction, the large yoke is replaced by a plurality of retaining blocks, these retaining blocks being mounted or set in cavities provided in the mold members, the retaining blocks being positioned so as to engage the outer surfaces of the side wall members when the mold is in the closed position.